Electrodes establishing electrical contact with the skin are used for the supplying electrical signals to the body as well as measuring electrical signals generated in or by the body.
Electrical signals may be supplied to the body of a patient through skin electrodes for various purposes, including the treatment of fibrillation by administering an electric shock, pain relief, and promotion of healing. The electric shock counteracts atrial or ventricular fibrillation of the heart, and, if the treatment is successful, makes the rhythm of the heart revert to the normal mode.
Electric signals generated in the body may be measured by skin electrodes and monitored on a suitable monitoring device. In particular, the electrical signals of the heart may be monitored on a electrocardiogram (ECG) to monitor the function of the heart.
Skin electrodes should meet a plurality of requirements to be suitable for supplying or measuring electrical signals, e.g. the skin electrodes must be sufficiently flexible to conform with the patient's body to secure a sufficient contact area, and to display satisfactory adhesion and electrical contact with the patient's body when the electrodes are placed properly.
A special requirement for a physiological electrode is that the electrode should withstand chemical and mechanical stress without deterioration. As electrodes are frequently a part of the standard emergency equipment used by rescue teams and in remote areas, the reliability of the electrodes may be crucial for saving lives. Furthermore, in the absence of a stabile and reliable electrode, the emergency equipment should be constantly controlled and old not used electrodes must be disposed of.
The electrically conductive layer of the physiological electrode may deteriorate during storing, handling or use resulting in a poor or absent electrical contact between the central area thereof and a wire connecting the electrode with an apparatus supplying or measuring electrical signals.
In EP 0 965 358 it is suggested to connect the electrically conductive layer with a sacrificial electrode prepared of a material more sensitive to corrosion than the material selected for the electrically conductive layer. While stored, the electrically conductive layer will remain unaffected, whereas the sacrificial electrode will deteriorate. While the use of a sacrificial electrode to a certain extent may protect the electrode from deterioration due to chemical attack, the electrode cannot operate satisfactory if the electrically conductive layer is broken.
In one aspect, the present invention aims at providing an electrode having the ability to withstand the chemical and/or mechanical stress which may occur during storage, handling and/or use. Especially, in a certain aspect of the invention, it is desired to provide an operable electrode having an electrically conductive layer exposed to corrosion.